Servo ram of the follow-up type



May 29, 1951 E. J. cARLET-ON SERVORAM oF THE: FoLLow-UP TYPE Fiied June 19, 194e 2 Sheets-Sheet 1 May 29, i951 E. J. cARLEToN sERvoRAM oF THE FoLLowmP TYPE y 2 Sheets-Sheet 2 Filed June 19, 1946 INVENTOR .IQI`\,

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Patented May 29, 1951 UNITED STATES PATENT OFFICE 2,554,614 simyo RAM oF THE FOLLOW-UP TYPE Emile J. Carleton, Holyoke, `Mass.

Application June 19, 1946, Serial No. 677,845

6 Claims. l

'This invention relates to an improved servo ram and more particularly to rams in vwhich the application of the operating hydraulic pressure is initiated and controlled `through hydraulic pressure supplied from a master control cylinder.

vThe principal object of the invention is to provide a ram of the above type which is positive in operation and in which the conditions of the resistance against which the ram is operating isperceptible to the operator of the lever or pedal by which the master lcylinder is controlled. l

Other and further o'bjects residing in the details of construction will be made apparent in the following specication and claims.

In the accompanying drawings which 'illustrate one embodiment of the invention,

Fig. 1 is a longitudinal sectional view, 4the parts being in inoperative position;

Fig. 2 is a fragmentary sectional View substantially on line 2-2 of Fig. 3; v

Fig. -3 is a transverse sectional View substantially on line 3-3 of Fig. 1;

Fig. 4 is a fragmentary sectional view substantiallyon line 4-4 of Fig. 3;

Fig. 5 is a sectional view "similar to Fig. 4 but showing the initial step in the operation of the ram;

Fig. 6 is a sectional view'similar to Figs. ``l and 5 showing `the parts in a 'further stage of operation; and

Fig."7 is a detail view of the chamber separat-V ing collar.

Referring to Fig. l `of the drawings the ram cylinder lis indicated at I0,fo ne end lb'eing closed by a cap member II secured to the cylinder 'by machine screws, one of which is shown-at I2. Operating in cylinder `I Il is a ram piston I3. 'Piston I3 is formed on its outer wall with an annular groove I4, the interior of the piston being hollow to form a chamber l5. The cap Vmember I I is formed with a hollow cylindrical portion I6 which extends part way into chamber I5, vand supports a valve operation `cylinder I'I which is press fitted .or otherwise secured rin the projection I6. The rear .end of cylinder Il' opens toa passage I8 `formed in Vcap member II, the .outer end of Vpassage .'I`8 Abeing threaded `as yat I9 to' receive any suitable pipe connection to the master cylinder M.

`Operating in 'cylinder Il is a valve piston 28, having a diameter D1, pinned to a forwardly projecting stem 2'I by a pin 22. Stem 2I extends through a collar 23 which is held against a shoulder 24, formed at the forward end Yof chamber I5, by a lock ring V2li. A spring 26 surrounding 2 Y, stern 2| and engaged between valverpiston 20 and collar 23 normally maintains valve piston 20 at the rear end or valve cylinder I'I.

Forwardly of collar l23 the central chamber of the ram is radially reduced "to 'form a valve chamber 22Tin which operates a valve plunger 28, which is of slightly 'less diameteLADa than piston 20. Plunger 28 is `sleciired to the forward end of stem 2`I by a snap ring `29. Collar 23 is provided withv openings 23 (see Fig. v7) to 'expose the rear vface of plunger `28 to the pressure in chamber vI 5. Two diam'etrica'lly opposite passages v30 connect chamber A2l lwith groove 'I4 'which in turn opens "to ay port 3| adapted. to be vconnected to asource of workinghydraulicpressure.` Plunger '2s is rormed with 'a Valve head '32 which 'in the inoperative position o'f Fig. 1 is positioned just forwardly 'of ports "30 so that hydraulic pressure entering groove I4 and chamber 21 i's balanced againsty the *rear 'face of 'head 32 and the opposite face of plunger'ZB aswell as in groove I4 so no movementis imparted to the valve head or to the ram.v

piston lf3.

Forwardly spaced from groove I4 the ram pistonla is reduced Vin diameter and rated with a cylindrical extension I33 forming with casing Illy an vannular chamber 34 'the 'forward end of which i's clos'ed 'by a short hollow Cylinder 35 fitting be' tween 'the extension 33 and casing I0. Cylinder 35 is held against rearward movement by a snap ring 36 and a 'suitable packing 3l is positionedl between cylinder '35 and an annular member 38f threaded at 39 into 'theend of the casing, there-v by 'rendering 'the end of chamber 34 uid tight.

Passages `"IIIJ connectjthe portion of chamber 2l forwardly of head 32 with chamber 34 and the latter opens 'to an exhaust port 4I adapted to,V be :connected toa sump or 'the low 'side o'f a pumpg Positioned "from passages 3'0 the forward portion -oi ram ncyl'in'clerj I3 'is provided, Fig. a, with passages T4.2 connecting 'the portion of chamber `2`I `forwardly Aof 'head 32 with the centrali chamber l5 of ram piston la. Thus in the moperative'position of the parts shown in Figs. 1, 2 and 3 'the chamber I 5 is open 'to the exhaust port 4I. 'Since Figs. 4, 5 and 6 are taken on a quarter,

as a stop to limit the forward movement of valve piston 20 and valve head 32 relative to the ram piston.

Referring to Fig. 5, when hydraulic pressure is admitted to the piston 20 through passage I8 valve stem 2| is moved forward against the pressure of spring 26, and head 32 is moved forwardly in chamber 21 thereby connecting passages 42 with chamber 21 at the same time shutting oi said passages 42 from the exhaust. Hydraulic pressure from power port 3| now enters chamber I5 through passages 30, chamber 21 and passage 42. I5 acts on the working surfaces of the ram cylinder, including surfaces 48 and 41, to move the ram piston forwardly and actuate whatever mechanism is operatively engaged by the working head 43. Fig. 5 shows the initial movement of the ram piston as valve piston 20 and valve head 32 are advanced to open passages 42 to the power port of the ram.

In Fig. 6 is shown the conditions when the piston 20 and valve head 32 have reached the forward limit of movement relative to ram piston I3; the head 32 being in engagement with the stop 45, and the ram piston has advanced a substantial distance in its working stroke.

Let us now consider the operating conditions at and between the positions of Figs. 4, 5 and 6. We will assume that passage I8 is connected to a master control cylinder having a hand or foot operated piston such as is used in the central control system of a power shovel, crane or similar apparatus. As will be seen from Fig. 4 the valve head 32 has a slight forward movement before passage 42 is closed to the exhaust and opened to the power port, the reaction against the pressure in control passage I8 being only that of spring 26. This condition changes as the passage 42 is partially opened to the power port, as in Fig. 6, and ram piston moves forward against whatever working resistance is acting on working head 43. As the power fluid, preferably oil, enters chamber I5 it acts against the forward annular face of valve piston 20 and the rear face of plunger 28. Since piston 20 is of slightly larger diameter than plunger 28 the pressure entering chamber I5 creates a resistance to the forward movement of valve piston 28 in addition to the load of spring 26, which increase is perceptible to the operator. The degree of this reaction may be adjusted or controlled by increasing or decreasing the difference between the diameters of plunger 28 and piston 20, with a consequent decrease or increase in the effective forward area of valve piston 20. This reaction from the pressure of the working fluid reaches its maximum when the full pressure of the working fluid is acting in chamber I5. A further change in condition takes place when the valve piston 20 and the valve head 32 are advanced to their foremost position, relative to ram piston I3, with head 32 engaging the stop 45, as shown in Fig. 6. This relative position of the parts is obtained either by an increase of the pressure in control passage I8 or by a slowing up of the ram piston due to an increasing resistance in the working load on working head 43. With valve head 32 engaged with stop 45, as in Fig. 6, the excess of the pressure in passage I8 over the load of spring 26 plus the back pressure on the forward annular face of piston 20 becomes in effect part of the working pressure on the working head and changes in the working load will be perceptible to the operator to a degree which is proportion- The hydraulic pressure entering chamberl ate to the proportion of the working load being carried by piston 20. For greater sensitivity this proportion may be increased by so dimensioning the valve plunger portion 28 that the latter throttle the power passages 30 when valve head 32 is in engagement with stop 45 and as it approaches such engagement, as is shown in Fig. 6.

Upon relief of the pressure in passage I8 spring 26 returns valve piston 28 and valve head 32 to the position relative to the ram piston shown in Fig. 4, thus opening chamber I5 to the exhaust and permitting the thrust on working head 43 to return the ram to the position of Fig. 1.

If during the forward movement of the ram piston I3 under the pressure admitted to the chamber I5 through passages 42 as in Figs. 5 and 6, the pressure in passage I8 is reduced to a point just sufficient to balance the pressure of spring 26 together with that portion of the pressure in chamber I5 acting with the spring, in other words if the stem 2I and the valve members 32 and 28 carried thereby are halted, the piston I3 will move forward relative to the stationary members 32 and 28 until the ports 42 overtake and are closed by the member 32, thus trapping the fluid in chamber I5 and halting further forward movement of piston I3.

With the parts in such position it will be seen that an increase or decrease of the pressure in control passage I8 will cause the member 32 to advance or retreat respectively, to respectively ,open port 42 to exhaust or pressure and thereby cause the piston I3 to resume its forward movement or to move rearwardly. Thus the piston I3 may be halted at any point in its forward or backward stroke by stopping the movement of member 32, the movement of which is controlled by the pressure in control passage I8.

The length dimension of the casing I0 and the travel therein of the ram piston I3 will of course be made such that the normal working stroke of the member operated by head 43 is within the length of exhaust chamber 34 so that the openings of exhaust passages 40 do not pass beneath the member 35 at the forward end of the working stroke of head 43. However, to assure the exhausting of chamber I5 when the valve piston returns to inoperative position, even if the exhaust openings 40 have been carried beneath member 35, I preferably provide grooves 48 extending rearwardly from the openings of passages 40 on the outer surface of the ram piston to maintain connection of the passages 40 with exhaust chamber 34 through a substantial range of over travel of the ram piston.

What I claim is:

- 1. A fluid pressure ram adapted to be controlled by a master cylinder, comprising in combination, a ram cylinder formed with a power port and an exhaust port, a ram piston reciprocably mounted in the ram cylinder, an end closure for the ram cylinder forming a pressure chamber at the rear of the ram piston, a valve member for selectively connecting said pressure chamber to the power port or the exhaust port ofthe ram cylinder, a fluid pressure valve operating cylinder having a valve piston reciprocably mounted therein Vof greater diameter than the diameter of the valve member, said valve piston being operably connected to the valve member, a spring normally maintaining said valve piston at the rear of the valve cylinder with the valve member connecting the pressure chamber to the exhaust port of the ram cylinder, a constantly'open passage from the pressure chamber to the opposed faces of the valve member and val-ve -piston `to admit pressure thereto only. when pressure lis admitted 4to the pressure chamber Lby the vvalve member, anda port inthe valveoperating -cylinder for admitting cdu'id :pressure `from lthe master cylinder to the rear vface of the valve Ipiston to actuate the valve member,

2. A fluid pressure ram comprising in combination, -a ram cylinder formed with a power port and an exhaust port, a ram vpiston reciprocably mounted in the ram cylinder, an 'end closure for the ram cylinder forming -a i.pressure Ichamber at the rear of the ram piston, azya'lve fmem'ber for selectively .connecting :said ,pressure chamber to the power port or the exhaust port of the ram cylinder', a fluid pressure valve operating cylinder "having a Valve piston reciprocably mounted therein of greatern diameter than the diameter ofthe valve member, said valve piston being operably connected 'to the valve member, a spring normally maintaining "said valve Apiston at the rear of the `valvecylinder with the valve member connecting the pressure chamber to the exhaust port of the ram cylinder, a constantly open passage from the pressure chamber to the opposed faces of the valve member and valve piston to admit pressure thereto only when pressure is admitted to the pressure chamber by the valve member, a port in the valve operating cylinder for admitting uid pressure to the rear face of the valve piston to actuate the valve member, and a stop member carried by the ram piston limiting the forward movement of the valve piston relative to the ram piston.

3. A Huid pressure ram comprising in combination, a ram cylinder formed with a power port and an exhaust port, a ram piston reciprocably mounted in the ram cylinder, an end closure for the ram cylinder forming a pressure chamber at the rear of the ram piston, a valve member for selectively connecting said pressure chamber to the power port or the exhaust port of the ram cylinder, a fluid pressure valve-operating cylinder having a Valve piston reciprocably mounted therein of greater diameter than the diameter of the valve member, said valve piston being operably connected to the valve member, a spring normally maintaining said valve piston at the rear of the valve cylinder with the valve member connecting the pressure chamber to the eX- haust port of the ram cylinder, a constantly open passage admitting pressure from the pressure chamber to the opposed faces of the valve member and valve piston when pressure is admitted to the pressure chamber by the valve member, a port in the valve operating cylinder for admitting fluid pressure to the rear face of the valve piston to actuate the valve member, and a stop member carried by the ram piston limiting the forward movement of the valve piston relative to the ram piston, the valve member being formed to partially throttle the flow of pressure fluid to the pressure chamber at the forward limit of movement of the valve piston relative to the ram piston.

4. A uid pressure ram comprising in combination, a ram cylinder, formed with a power port and an exhaust port, a closure member closing one end of the cylinder, a ram piston reciprocably mounted in the cylinder, a pressure chamber formed in the rear portion of the ram piston and opening toward said member, a valve cylinder extending forwardly from said member part way into the pressure chamber, the forward end of said valve cylinder opening to the pres- 6, sure c'hambena valve chamber vformed in the forward 'part of the ram piston, a passage through the ram piston connecting the valve chamber to the power por-t of the ram cylinder, a passage through the ram piston connecting the valve chamber to lthe exhaust port of the ram cylinder, a passage in the ram piston connecting the valve chamber with the pressure chamber, a valve member including a valve head reciprocably mounted in the valve chamber, the rear face of the valve member being exposed to the pressure chamber, a valve piston reciprocably mounted in the :valve cylinder and a stem connecting -said valve member and valve piston, said valve piston being -of greater -diameter than the valve member to expose `a greater area tothe pressure chainber, said valve head when in the rear portion of the -Va-lve chamber opening the pressure chamber to the exhaust port and when in a forward portion .of the valve chamber opening the pressure chamber-'to the power port, a spring normally maintaining the valve member in its rearmost position, and a passage, opening through said closure member to the rear face of the valve piston for admitting uid pressure to the valve cylinder.

5. A fluid pressure ram comprising in combination, a ram cylinder, formed with a power port and an exhaust port, a closure member closing one end of the cylinder, a ram piston reciprocably mounted in the cylinder, a pressure chamber formed in the rear portion of the ram piston and opening toward said member, a valve cylinder extending forwardly from said member part way into the pressure chamber, the forward end of said valve cylinder opening to the pressure chamber, a valve chamber formed in the forward part of the ram piston, a passage through the ram piston connecting the valve chamber to the power port of the ram cylinder, a passage through the ram piston connecting the valve chamber to the exhaust port of the ram cylinder, a passage connecting the valve chamber with the pressure chamber, a valve member including a valve head reciprocably mounted in the valve chamber, the rear face of the valve member being exposed to the pressure chamber, a valve piston reciprocably mounted in the valve cylinder and a stem connecting said valve member and valve piston, said valve piston being of greater diameter than the valve member to expose a greater area to the pressure chamber, said valve head when in the rear portion of the Valve chamber opening the pressure chamber to the exhaust port and when in a forward portion of the valve chamber opening the pressure chamber to the power port, a spring normally maintaining the valve member in its rearmost position, a passage, opening through said closure member to the rear face of the valve piston for admitting fluid pressure to the valve cylinder, and a stop member carried by the ram piston and engageable by said valve head to limit the forward movement of the valve member relative to the ram piston.

6. A iluid pressure ram comprising in combination, a ram cylinder, formed with a power port and an exhaust port, a closure member closing one end of the cylinder, a ram piston reciprocably mounted in the cylinder, a pressure chamber formed in the rear portion of the ram piston and opening toward said member, a valve cylinder extending forwardly from said member part way into the pressure chamber, the forward end of said valve cylinder opening to the pressure chamber, a valve chamber formed in the forward part of the ram piston connecting the valve chamber to the power port of the ram cylinder, a passage through the ram piston connecting the valve chamber to the exhaust port of the ram cylinder, a passage connecting the valve chamber with the pressure chamber, a valve member including a valve head reciprocably mounted in the valve chamber, the rear face of the valve member being exposed to the pressure chamber, a valve piston reciprocably mounted in the valve cylinder and a stem connecting said valve member and valve piston, said valve piston being of greater diameter than the valve member to expose a greater area to the pressure chamber, said valve head when in the rear portion of the valve chamber opening the pressure chamber to the exhaust port and when in a forward portion of the valve chamber opening the pressure chamber to the power port, a spring normally maintaining the valve member in its rearmost position, a passage, opening through said closure member to the rear REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,130,177 Kramer Mar. 2, 1915 2,260,491 Stelzer Oct. 28, 1941 2,322,063 Schnell June 15, 1943 2,374,545 Ingres Apr. 24, 1945 2,410,269 Chouings Oct. 29, 1946 2,450,160 Price Sept. 28, 1948 

